Process for the manufacture of aluminium nitrid.



0.4 SERPEK. 1111003518 PoR THE MANUPAOTURE 0F ALUMINIUM NITRID.

APPLICATION FILED JUNE 21. 1910.

Patented June 20, 1911.

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rAnIs,"raANcn, AssIGNoR T01 SOCIT GENERALE Das NITRURES, vOIE PARIS,FRANCE.

PROESS FOB. THE MANUFACTUBE ALUMINIUM NITRID.

Specification of Letters Patent. Patented J 1111115 20, 1911,

Application led une 21, 1910. Serial No. 568,159.

To all whom 'it may concern.' A

Be it known that I, OTTOKAR SERPEK, a subject of the Emperor ofiAustria-Hun! gary, and a resident of 12 Rue Roquepine, Paris, France,have invented a new and useful Process for the Manufacture of AluminiumNitrid, of which the following is a specification.

The present invention relates to an apparatus for the manufacture ofaluminium nitrid, by the method which consists in the fixation ofnitrogen by alumina bauxite, or other aluminium ores in presence ofcarbon at a high temperature.

The object of the invention is to obtain aluminiumnitrid practicallyfree from carbids or silicon compounds and at the same time to reduce toa minimum the quantity of heat expended. This object is attained bycarrying out the reaction properly so-called by electrical heatingwhereas the preliminary heating of the substances is effected by thecombustion of the carbon monoxid which is developed in the. reaction andof that which is formed by the gas-generator supplying the necessarynitrogen, while Ithe preliminary heating of the gases takes place by thecooling of the nitrid as it leaves the electric furnace.

The principle of the apparatus is here-l after described with referenceto the annexed diagrammatic drawing.-

The apparatus employed for the manufacture consists of two revolvingcylinders a 5 similar to those used in the cementindustry. These twocylinders both enter at one extremity aixed chamber c. The uppercylindera is a bauXite-calciner, heated lby gas as hereafter described. Thelower cylinder b is similar to the preceding except that in the part d ethere is inserted an electrical resistance-.furnace f, preferably of thetype described in my application for Patent No. 568158 filed June 21,1910. This furnace is made detachable so that it is readily retheresistanoes and the furnace has to be renewed long before the tubes a bare worn out. The extremity g of the cylinder b leads to a fixed chamberz. which also receives through a passage z' the gases from a retort orgenerator j working under pressure.

The extremity k of the cylindera is arrangedto serve for the removal ofthe gases burned in this cylinder-and for the supplying of the bauxite.

In the chamber 0 a partition l forms' witl the walls of this chamber ahopper mf of which the contents press upon the head n of the cylinder b.This hopper receives the bauxite which has been calcined in the uppercylinder a, and it also receives through v the opening o powdered cokestoredv in the hopper p'. The head n -is provided with an' opening nserving for the escape of the heated gases coming from the cylinder b,and with openings q of suitable number and dimensions for'the passage ofthe contents of the hopper m into this cylinder.

The operation is as follows: Ground bauxite is introduced through theopening lc into the upper part 'of the cylinder a, and descends slowlyalong this tube by reason of the slope and the rotary motion; it fallsat length through the opening 1' into the compartment m. In thiscompartment it mixes with carbon from the hopper p, and the mixturepasses through the vopenings g into the lower cylinder b. The rotationof this cylinder, while conveying the mixture to the electrical part ofthe furnace where the reaction proper is to take place, acts to mix thebauxite and carbon intimately together.

In the section dye which consists as stated.v

of an electrical resistance-furnace, the reaction takes place whichgives rise to the nitrid. The nitrogen necessary to the reaction isfurnished by the gas from the generator y', and this gas is itselfgreatly enriched in carbon monoxid by the reaction itself. This enrichedgas leaves by the opening n. passing into the chamber c and taking withit in the form of more or lessl complex com pounds the greater part ofthe silica of the heated4 material. In 'the chamberV c there may beproduced by a suitable blast of air as at c a partial combustion of thegas resulting-in the oxidation of these compounds and their deposit inthe form of silica. placed, for there is considerable wear upon Battlingpartit-ions s may be arranged to facilitate this deposit'. At thel topof the chamber c the gases ass through the opening 1' into the cylin era, after having received by more forced air inlets c2, c3, c* the oxygennecessary to their complete combustion in this upper part of the chamberand in the cylinder a, itself. This combustion supplies the heatnecessary to the calcination of the bauxite in the cylinder a. If it bedesired to increase the temperature in the upper tube, combustible gasesor powdered fuel may be introduced at c2, c at the same time as the air.Instead of supplying bauxite alone to this tube, the mixture of bauxiteand carbon may be supplied; in this latter case the hopper p servesmerely for the addition of the carbon necessary to compensate for thecombustion 0f carbon in the upper tube during the calcination.

As regards the temperature employed and the methodical recovery of theheat, the following results are obtained: The mixture of nitrogen andcarbon monoxid leaves the generator already at a high temperature (about400o C.) and is further heated While ascending the tube b in contactwith the nitrid which leaves the electric furnace at temperatures of18000; when it escapes to the chamber c it is about 2000. The gases aremore effectively heated for the reason that the rotation of the furnacecauses a constant stirring into contact with the gases of the solidsubstances which are at a high temperature. In the electric furnace, themixture of carbon and bauxite is already heated on arrival, and thenitrogen acting upon it produces aluminium nitrid. The rotation ofthefurnace causes a stirring of the material, and at the same time thesolid particles in falling constantly in an atmosphere containingnitrogen offer to this latter a larger and constantly renewed surfacefor attack.

Upon leaving the furnace the hot gases are in contact with the solidsubstances and as a result they strongly heat the latter. At the top ofthe chamber 0 the gases encounter an air inlet, which by reason of theirvery high temperature (about 1500O C.) permits the combustion of thecarbon monoxid. Consequently their temperature is again further raisedand as they pass through the tube or cylinder a in the contrarydirection to the bauxite they effect the calcination of the latter. V1nthe same way as in the lower part of the tube b, the stirring caused bythe rotation favors the exchange of heat between the gases and thebauxite which attains a temperature of 1400O C. when it falls at m,while the gases leave the top of the tube a at about 300- centigrade.

This arrangement therefore affords a number of advantages. (l) Amethodical heating of the substances takes place with as completerecovery of the heat as possible. (2) For this heating there is utilizedthe combustion of combustible gases produced in the generator and in theelectric furnace; the quantity of heat to be furnished by the electricalenergy is thereby reduced to a minimum. (3) The solid substances aremixed in an intimate manner before entering the electrical furnace. (4).An intimate contact of all the articles withthe nitrogenous atmosphere1n the furnace is insured. (5) The silicon contained in the bauxite andvolatilized in the electrical furnace is separated by combustion and bythe deposit in the chamber c of the silica so formed. (0) It becomespossible to calcine the bauxite before mixing itwith carbon, and so toavoid any loss of carbon during the calcination.

The invention is not strictly limited to the arrangement indicated,which may be modi` tied as practice-may show to be necessary; inparticular the arrangement for feeding the carbon and bauxite mixture totheI lower tube and the arrangement allowing the combustion and theseparation of the silicon are given merely by way of example. In thesame way this apparatus may be employed for the manufacture of othermetallic nitrids from oxids capable of being treated under similarconditions, with suitable modifications as required.

Claims:

`l. An apparatus for the manufacture of aluminium nitrid comprising astationary vertical chamber, a revolving inclined cylinder opening atits lower end into the upper portion of said chamber, a second inclinedrevolving cylinder openingat its upperend into said chamber at a lowerlevel than said first cylinder, means for feeding ore from saidupper tosaid lower cylinder, in combination with an electric resistance furnacearranged in said lower cylinder and means for leading a suitable gas tosaid lower cylinder and furnace and thence to the upper cylinder, saidintermediate chamber having ports arranged therein to admit air whichaffords the oxygen necessary to the combustion of said gas in the uppercylinder, substantially as described.

2. rn apparatus for the manufacture of aluminium nit-rid, comprising astationary vertical chamber, revolvinginclined cylinders opening intosaid chamber one above the other at their lower and upper endsrespectively, in combination'with a hopper arranged within said chamberto receive the discharge from the upper cylinder and guide it to thelower cylinder, and a hopper external to vsaid chamber but communicatingwith the hopper within said chamber to permit the addition of othermaterial to the charge entering the lower cylinder, together with anelectric furnace in said lower cylinder and means for leading to thelatter and thence to said chamber and upper cylinder a suitable gas,substantially as described.

3. An apparatus for the manufacture of aluminium nitrid comprising twooppositelyv inclined rotating cylinders communicating at one 4endthrough an intermediate chamber, said lower cylinder receiving at leasta portion of its charge from said upper cylin- 130 der, in combinationwith an electric resistance furnace rigidly mounted in said lowercylinder and revolving therewith, together with means for leading asuitable gas to said lower cylinder and furnace and thence to the uppercylinder, substantially as described.

4. An apparatus for the manufacture of aluminium nitrd,comprising twooppositely inclined rtating cylinders communicating at one endV throughan intermediate chamber, said lower cylinder receiving at least aport-ion of its charge from Said upper cylin-v der, in combination withan electric furnace in said lower cylinder and means for leading asuitablereaction gas to said lower cylinder and furnace, together with abaffled passage for said gas from said lower cylinder to the uppercylinder and a port for the admission of air to mingle with said gasbefore reaching the bailes in vsaid passage, for the purpose specified.

5. An apparatus of the character described comprising as an elementthereof a rotary conveying cylinder carrying an electric resistancefurnace through which the material treated is passed.

6. An apparatus for the purpose described comprising a calciningcylinder, a

' reaction furnace and means for leadingthe discharge from saidcalcining cylinder to said furnace, in combination with means forleading a reaction gas' through said furnace to said calcining cylinder,together with an air intake interposed between said furnace andcalcining cylinder -for supporting the combustion of said gases in thecalcining cylinder.

7. An apparatus forA the purpose described, comprising a calciningcylinder, a mixing hopper into which said calcining cylinder discharges,a reaction furnace and means for 'leading' the material from said hopperthereto, in combination with means for leading a reaction gas throughsaid furnace and`past said hopper to the calcining cylinder, togetherwith an air intake interposed between said furnace and cylinder forsupporting the combustion of said gas in the calcining cylinder,substantially as described. f

8. An apparatus of the character described, comprising as an elementthereof a rotary conveying cylinder with an electric resistance furnacedetachably mounted therein intermediate its ends, substantially asdescribed.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses.

OTTOKAR4 SERPEK.

Witnesses; v

CHARLES DONY, JAQUES LIGNEY.

